A vehicle includes exterior sub-assemblies including exterior panels that may be formed from metal, such as steel, and may be manufactured by various metalworking processes. Some components of the vehicle include an interior panel, typically formed of metal, and the exterior panel may be hemmed to the interior panel. For example, vehicle components such as doors, a hood, a deck lid, and a moon roof may each include the exterior panel hemmed to the interior panel. The interior panel may, for example, include attachment points for hoses, wires, etc., and may structurally reinforce the exterior panel.
To fabricate the exterior panel, a metal sheet blank may be formed by one or more stamping dies. For example, the blank may be moved between several stamping dies in a stamping line. The stamping line may include a draw die that shapes the blank, a trim die that trims exterior extra material from the periphery the panel, and a flanging die that forms a flange around at least a periphery of the panel.
After the flange is formed, a hemming operation hems the flange of the exterior panel around an edge of the interior panel. Specifically, the interior panel and the exterior panel are placed on a hem die and the flange is bent around the edge of the interior panel. For example, a pre-hem tool may bend the flange about the edge of the interior panel and a hemming tool may shape and compress the flange about the edge of the interior panel. This hemmed flange reinforces the edge of the exterior panel, hides burrs and rough edges, and provides an aesthetically pleasing appearance.
These various steps on the stamping line and the hemming die each contribute to the final shape of the sub-assembly. One or more of these steps, individually or in combination, affect the size, shape, and location of the flange. The size, shape, and location of the flange affects the gap size between two adjacent panels, e.g., the gap between a front door and a rear door of the vehicle. The aesthetic appearance of the vehicle may be negatively judged when these gaps are large. As such, it is beneficial to reduce the size of these gaps to render a more aesthetically pleasing appearance of the vehicle. Attempts to minimize the gap size between the panels are typically made by trial-and-error and each attempt is time consuming and costly. In addition, one change made during the trial-and-error process may inadvertently and undesirably change another feature of the panel.
In addition the various steps on the stamping line and the hemming die, individually or in combination, may cause non-conformities in the exterior panel, e.g., defects. For example, the hemmed flange is preferably smooth and the non-conformities may include wrinkling, cracking, creepage, creasing, etc., along the flange. Attempts to correct these non-conformities may be made by adjusting the dies in the stamping line and/or adjusting the pre-hem tool or the hemming tool. Such adjustments to the stamping line, the pre-hem tool, and/or the hemming tool are also typically made by trial-and-error and each attempt is time consuming and costly. As such, the fabrication of the dies in the stamping line, the pre-hem tool, and the hemming tool is costly and time consuming. Accordingly, there remains an opportunity to improve the fabrication of the stamping line, the pre-hem tool, and the hemming tool.